Dynamic beam convergence system for tri-color kinescopes



United States Patent Ofiice DYNAMIC BEAM CONVERGENCE SYSTEM FOR TRI-COLOR KINESCOPES John Stark, Jr., Woodbury, N. J., assignor to Radio Corporation of America, a corporation of Delaware Application May 27, 1953, Serial No. 357,843 11 Claims. (Cl. 315-13) This invention relates to systems for controlling the electron beam energy of cathode ray tubes. It pertains particularly to the control of a plurality of electron beam components used in television kinescopes so as to effect substantial convergence of the components at all points of a raster scanned at a target electrode.

One type of cathode ray tube in which there is encountered the problem of maintainingsubstantial convergence of a plurality of beam components at a target electrode is a color kinescope such as that disclosed in a paper by H. B. L w titled A Three-Gun Shadow-Mask Color Kinescope published in the Proceedings of the IRE, vol. 39, No. 10, October 1951 at page 1186. Such a tube has a luminescent screen consisting of a multiplicity of phosphor areas of sub-elemental dimensions. Different ones of the phosphor areas are capable of producing light of the component image colors when excited by electron beam energy. In this tube, the different light-producing phosphor areas are excited respectively by a plurality of electron beams, or by a plurality of components of a single beam, approaching the screen from different angles through an apertured electrode. Color selection is se cured by the angle at which the electron beam components approach the screen. A tube of the kind described forms the subject matter of U. S. Patent 2,595,548 granted May 6, 1952, to Alfred C. Schroeder for Picture Reproducing Apparatus.

The expression electron-beam components as used in this specification and claims will be understood to denote the phosphor-exciting electronic energy produced either by a single, or by a plurality of, electron guns. This energy may be continuous or pulsating as required without departing from the scope ofthe invention. An example of a color kinescope in which diflerent components of a single electron beam are used to excite a phosphor screen of the kind described is disclosed in a paper by R. R. Law, titled A One-Gun Shadow-Mask Color Kinescope published in the Proceedings of the IRE, vol. 39, No. 10, October 1951, at page 1194. Such a tube forms the subject matter of a copending U. S. application of Russell R. Law, Serial No. 165,552, filed June 1, 1950 and titled Color Television.

The successful operation of a multi-color kinescope of the type referred to requires that the plurality of electron beam components be made to converge substantially at the apertured electrode at all points in the scanned raster. In view of the fact that the different points of such a target electrode are at different distances from the point or region of the electron beam deflection, it is necessary to provide a field-producing means which is variably energized to produce the desired dynamic convergence control. One such electron beam control system is disclosed in a paper by Albert W. Friend titled Deflection and Convergence in Color Kinescopes" published in the Proceedings of the IRE, vol; 39, No. 10, October 1951 at page 1249. Such a system forms the subject matter of a copending U. S. application of Albert W. Friend, Serial No. 164,444, filed May 26; 1950, and'titled Electron Beam Control System. In the system proposed by Friend, electron-optical apparatus is energized both statically and dynamically to produce the desired result. By means including the static energization of the electronoptical apparatus, the Friend system effects initial convergence of the electron beam components substantially at the center of the raster to be scanned. The dynamic energization of the electron-optical apparatus is effected as functions of both the horizontal-and vertical beam deflection. Essentially these functions are parabolic.

'The term static energization of the electron-optical beam convergence apparatus, as used with reference to the Friend system and in the following specification and claims, denotes the effective D.-C. energization of this apparatus whereby initial beam cenvergence is effected. The term dynamic energization of the beam convergence apparatus, similarly, denotes the effective A.-C. energization of this apparatus whereby beam convergence is maintained for all angles of beam deflection as the raster is scanned.

It is an object of this invention to provide improved and simplified apparatus by which to develop waveforms for the dynamic energization of an electron beamcontrolling system for a multi-beam kinescope.

Another object of the invention is to provide improved apparatus by which to develop waveforms for effecting dynamic convergence of the electron beam components of a multi-beam kinescope, the apparatus being of such a character that the waveforms may be impressed upon the convergence apparatus with a minimum of coupling components.

In accordance with this invention there is provided wave-generating apparatus having an input circuit which may be coupled directly to the deflection apparatus and which requires no appreciable additional amplification so that it may be coupled to the field-producing electronoptical apparatus by means of which beam convergence is to be effected. The apparatus embodying the invention comprises a convergence wave output transformer having its primary winding coupled to the cathode circuit and/or anode circuit of an electron tube serving as the output stage for one of the electron beam deflection waves by means of which the electron beams are deflected to scan the usual rectangular raster at a target electrode. The secondary winding of the convergence transformer is coupled to the field-producing, or electron-optical, apparatus for the dynamic energization thereof, whereby to effect the desired electron beam convergence. The secondary transformer winding coupling includes an electron tube used as a shunt regulator for the static convergence voltage impressed upon the convergence apparatus.

The novel features that are considered characteristic of this invention are set forth with particularity in the appended claims. The invention itself, however, both as to its organization and method of operation, as well as additional objects and advantages thereof, will best be understood from the following description when read in conjunction with the accompanying drawing, in which:

Figure 1 is a circuit diagram, mostly in block form, except for the illustrated details of the apparatus em bodying the present invention, for developing a beam convergence wave for use with electron-optical beam converging apparatus of an electrostatic type; and,

Figure 2 is a fragmentary circuit diagram of that portion of the'dynamic convergence wave-producing apparatus embodying another form of this invention.

Reference first will be made to Figure 1 of the drawing for a description of an illustrative embodiment of the invention. The television receiver represented in this figure is generallyconventional and includes an antenna l lto which is coupled a conventional television signal receiver 12. It will be understood that the receiver 12 Patented Dec. 6, 1955 may include such usual apparatus as carrier wave amplifiers at both radio and intermediate frequencies, a frequency converter and a carrier wave demodulator or signal detector. Accordingly, it will be understood that there are derived from the receiver 12 the video and synchronizing signals. The video signals derived from the receiver 12 are'impressed' upon a video signal channel 13 and the synchronizing signals are impressed upon a sync signal separator 14. The video signal channel is coupled to the usual electron beam control apparatus, customarily referred to as electron gun apparatus, of an image-reproducing device such as a color kinescope 15.

In the illustrative embodiment of the invention, it is assumed that the kinescope is of the same general type disclosed in the H. B. Law paper previously referred to. It will be understood, however, that the kinescope alternatively may be of other types such as that shown in the aforementioned R. R. Law paper. In any case, the kinescope has a substantially flat luminescent screen 16 which is provided with a multiplicity of small phosphor areas arranged in groups and capable respectively of producing light of the diiferent primary colors in which the image is to be reproduced when excited by electron beam energy. In back or", and spaced from the screen 16, there is an apertured masking electrode 17 having an aperture for, and in alignment with, each group of phosphor areas of the screen 16. In the particular tube illustrated, the kinescope also has a plurality of electron guns 18, 19, and 20, equal in number to the number of primary colors in which the image is to be reproduced. As previously indicated, these three electron guns 18, 19, and 20 are coupled to the video signal channel 13 for respective control by video signals representing the three primary colors, such as red, green, and blue, in which the image is to be reproduced. It will be understood that each of these guns may be conventional consisting of a cathode, a control grid, and a first anode, or beam-forming electrode. Also associated with the three electron guns are corresponding individual beam-focusing anodes 22, 23 and 24. The three electron guns 18, 19 and 20, together with their associated focusing electrodes 22, 23 and 24 respectively, function to develop respective electron beams 25, 26 and 27 which are caused'to approach the target electrode structure, including the luminescent screen and the masking electrode 17, from three different angles which, for convenience, have been shown greatly exaggerated in the drawing. By means of the different angles of approach these beams are caused to excite the different colored light-producing phosphors. The color kinescope 15 additionally is provided with an electro-static type of beam-converging apparatus which includes a convergence anode 28 located adjacent to the paths followed by the electron beams in the pre-deflection region. The kinescope also includes the usual final, or beam accelerating, anode 29 generally in the form of a wall coating substantially as shown and extending from the pre-defiection region adjacent to the convergence anode 28 tothe vicinity of the target electrode structure including the screen 16.

The different static potentials which are impressed upon the various kinescope electrodes are derived from'a high voltage power supply 30, which may be of the flyback type such as shown in U. S..Patent No. 2,074,495'granted March 23, 1937, to A. W. Vance and titled Circuits for Cathode Ray Tubes. The individual beam-focussing electrodes 22, 23 and 24 are connected together and to a relatively low positive potential point (e. g. 3500 volts) of the power supply 30. The convergence anode 28 is coupled by means including a voltage divider'or bleeder resistor 31 to a somewhat higher positive potential point of the high voltage power supply. By such means the con-' vergence anode has impressed thereon a potential of approximately 5500 volts so that, as a result of the potential difference between it and the individual beam focussing anodes 22, 23 and 24, there are produced electrostatic electronroptical lenses by which individual beam focussing is effected. In a like manner, the final anode 29 is connected to a still higher positive potential point (e. g. 27,000 volts) of the high voltage power supply. It will be understood that the high voltage necessary for impression upon the final anode 29 may be conveniently derived by means of a voltage doubler coupled to such a point as the high potential end of the bleeder 31 connected in the circuit supplying energizing potentials to the convergence anode 28. Also, it will be understood that the potential which is impressed upon the individual beam focussing electrodes 22, 23 and 24 may be provided from a separate power supply of the flyback type, if desired. Inasmuch as arrangements of this character form no part of the present invention, they have not been shown in detail. The purpose of the electron-optical device including the convergence anode 28 and the final anode 29 is to produce the desired convergence of the individual electron beams substantially in the plane of the apertured electrode 17..

The color kinescope 15 also is provided with apparatus by which to deflect the plurality of electron beam components both vertically and horizontally to scan the usual raster at the luminescent screen 16. In this embodiment of the invention the deflection apparatus includes a yoke 33 which in general is of a conventional type. It consists of a pair of interconnected coils forming a horizontal deflection winding and another pair of coils forming a vertical deflection winding. The yoke is mounted around the neck' of the kinescope in the region adjacent to the point at which the neck joins the conical section of the tube.

The horizontal and vertical windings of the yoke 33 are energized by conventional apparatus. The sync signal separator 14, which separates the sync signals from the video signals andfrom one another produces horizontal and. vertical frequency sync signals respectively in its output circuits H and V. The horizontal output circuit H is coupled to a horizontal sweep oscillator 34, the output of which, in turn, is coupled to the input circuit of a horizontal sweep output apparatus 35 for the impression thereon of a substantially sawtooth wave 36 at horizontal deflection frequency. Both of these horizontal sweep components may be entirely conventional. The output circuit of the horizontal sweep output apparatus 35 is coupled to the horizontal deflection winding of the yoke 33 in the customary manner.

v The vertical sync separator output circuit V is coupled to a vertical sweep oscillator 37 which produces in its output circuit a substantially sawtooth wave such as 38 at the vertical deflection frequency. The output of thevertical sweep oscillator is coupled to the input circuit of a vertical sweep output stage including an electron tube 39. This tube may be a pentode, such as a 6K6-GT, or a beam power tetrode, such as a 6U6 or its miniature equivalent a 6AQ5, or other similar tube types which'are extensively used in conventional vertical sweep output apparatus. The anode of the vertical output tube 39at-which a sawtooth wave 38 is developed, is coupled to the primary winding 40 of a vertical deflection waveoutput transformer, also as is customary in such systems. The secondary winding 41 of the vertical output transformer is connected to the vertical deflection winding of the yoke 33. A bypassed variable cathode resistor 42 serves as a linearity control of the vertical deflection wave. Also, at the cathode of the vertical output tube 39, there is developed a substantially parabolic wave 43 atvertical deflection frequency. Similarly, a similar oppositely phased parabolic wave 43' is developed across the b'ypassed decoupling resistor 32 in the anodecircuit of. the. tube 39.

Thesezparabolic waves 43 and 43 are impressed upon opposite ends of the primary winding 44 of a vertical convergence transformer 45 by means of an A.-C. coupling, including-a capacitor 46, to the cathode and anode circuits of the vertical output tube 39. It is seen that, by virtue of this A.-C. coupling, the primary transformer winding is not required to conduct any of the D.-C. component appearing in the cathode circuit of the vertical output tube.

The parabolic waves 43 and 43' are substantially reproduced in the secondarywinding 47 of the vertical convergence transformer 45. Theimpedances of the transformer circuits are such that the parabolic wave energy is slightly differentiated as it is developed in the secondary winding 47.

The secondary winding 47 of the vertical convergence transformer has connected in parallel therewith a series arrangement of a capacitor 48 and a variable resistor 49. By means of the capacitor 48 and resistor 49, an adjustable amount of integration of the substantially parabolic wave form developed in the secondary winding 47 may be effected. In this way, the substantially parabolic wave may be suitably shaped for use in controlling the dynamic beam convergence of the kinescope 15.

The secondary winding 47 of the vertical convergence transformer 45 also is shunted by the resistance element of an output potentiometer 50. The movable contact of the potentiometer is coupled to the cathode of a voltage regulator electron tube 51. The tube 51 functions primarily as a shunt regulator for the high static voltage impressed upon the convergence anode 28 of the kinescope 15.

An intermediate point of the bleeder resistor network 31 is connected to the convergence anode 28 of the kinescope so as to impress thereon the necessary static potential for effecting a static convergence of the electron beams 25, 26, and 27 as previously described. For the successful operation of the beam convergence system, it is desirable to maintain this static potential relatively constant. Accordingly, the regulator tube 51 is effectively shunted across the portion of the bleeder network 31 in which the convergence static potential is developed. In order that the shunt regulator tube 51 perform its function, the control grid thereof is connected to a point on the bleeder network so as to make the shunting action of the regulator tube 51 responsive to any varying tendency of the voltage developed across that portion of the bleeder which supplies the convergence static potential. A potentiometer 53 connecting the cathode circuit of the regulator tube 51 to different potential points (e. g. 400 and 600 volts, respectively) of a low voltage power supply 52 is adjustable for the purpose of making the proper adjustment of the static potential applied to the convergence anode 28.

By means of the described circuit coupling the vertical convergence transformer 45 and the convergence anode 28 of the kinescope 15, it is seen that a suitably shaped parabolic wave 54 at vertical deflection frequency is developed at the anode of the shunt regulator tube 51 for impression upon the beam convergence system for the dynamic control thereof at vertical deflection frequency. The injection of this convergence control wave into the cathode circuit of the shunt regulator tube 51 provides a relatively simple and effective means for impressing the desired convergence controlling wave upon the electron-optical apparatus of the kinescope 15. The amplitude of the vertical dynamic convergence wave 54 is controlled by the setting of the output potentiometer 50.

The complete beam convergence controlling system, of which the present invention is a part, includes a horizontal convergence control wave generator 55 which is coupled as indicated for control to the output of the horizontal sweep oscillator 34. This apparatus may be substantially in accordance with that disclosed in the Friend paper previously referred to. Accordingly, it will be understood that this generator functions to produce a substantially parabolic wave 56 at horizontal deflection frequency for impression, by means such as a coupling capacitor 57, upon the convergence anode 28 of the color kinescope 15. 7

Reference now will be made to Figure 2 of the drawing for a description of another form of apparatus in accordance with the present invention. It will be under-. stood that this apparatus may be substituted in the circuit of Figure 1 at the input terminals A and B and output terminals C and D. In this case, the vertical convergence output circuit includes two transformers 58 and 59. The primary winding 60 of the parabolic wave transformer 58 is coupled by means including a capacitor '61 to the input terminals A and B. In this manner, the primary winding is traversed by the substantially parabolic waves 43 and 43'. The secondary winding 62 of the parabolic wave transformer 58 is shunted by an integrating capacitor 63 and develops a substantially parabolic output wave 64.

The primary winding 65 of the sawtooth wave transformer 59 is shunted by a potentiometer 66, the adjustable contact of which is coupled by a capacitor 67 to terminal A and the center tap of which is connected to the center tap of the primary winding 65 and also to the input terminal B. In this manner, as determined by the setting of the potentiometer 66, a variable amplitude component of a sawtooth wave 69, corresponding substantially to the deflection sawtooth wave 38, is impressed upon the primary winding 65 of the sawtooth transformer 59. The parameters of the primary winding circuits including the potentiometer 66 and the coupling capacitor 67 are such that the parabolic waves 43 and 43' are diiferentiated to form the sawtooth wave 69. Also, by means of the described center tap connections of the primary winding 65 and the potentiometer 66, it is seen that the polarity of the sawtooth wave 69 may be reversed. Accordingly, there is developed in the secondary winding 68 of the sawtooth transformer 59 a substantially sawtooth wave 69 of the desired amplitude and polarity.

The secondary windings 62 and 68, respectively, of the parabolic and sawtooth wave transformers 58 and 59 are connected in series across the output potentiometer 50. It is seen that by this arrangement there is produced at the output terminals C and D a substantially parabolic wave, as in the case of the apparatus of Figure l, which is shaped in the desired manner by means of an additional sawtooth wave component for impression upon the convergence apparatus of the color kinescope 15. This shaping is effected by a suitable manipulation of the potentiometer 66. The amplitude of the composite convergence wave is controlled, as in the former case, by the adjustment of the output potentiometer 50.

It may be seen from the foregoing description of a number of illustrative embodiments of the invention that there is provided improved and simplified apparatus by means of which the necessary wave forms, particularly at vertical deflection frequency, may be developed for the dynamic energization of the convergence apparatus of a color kinescope. This apparatus is of such a character that the wave forms may be impressed upon the kinescope convergence apparatus with a minimum number of components and with a minimum of interference with other functions of the control apparatus for the kinescope.

Specifically, it is seen that no additional electron tubes, are required, either for the development of the waves or for the coupling of the waves to the convergence apparatus. By using the shunt regulator tube of the convergence high voltage system as a grounded grid amplifier, it is seen that the vertical dynamic convergence voltage wave is effectively added to the regulator circuit and from thence to the convergence apparatus of the kinescope. The addition of the convergence wave to the regulator circuit is effected in such a way as to in no way interfere with the relatively critical leakage resistance requirements'of the bleeder network of the regulator. Furthermore, this matter of injecting the convergence 7 control wave into the voltage regulator circuit does not add any time constant components which would tend to slow up the speed of the regulation.

The nature of the invention is described "in the foregoing specification. The scope of the invention is set forth in the appended claims.

What is claimed is:

1. In a cathode ray image reproducing system wherein a plurality of electron beam components, which traverse predeflection paths that are spaced respectively about the longitudinal axis of a tube, are angularly deflected both horizontally and vertically by deflection apparatus to scan a raster at a target electrode and having fieldproducing apparatus adjacent to said predeflection patn's and energizable to effect substantial convergence of said beam components at all points of said raster, a system to energize said beam convergence field-producing apparatus comprising, a raster scanning substantially sawtooth deflection wave generator coupled to said deflection apparatus, a source of static convergence voltage coupled to said convergence field-producing apparatus, a voltage regulator coupled to said static convergence voltage source, and means coupled between said sawtooth deflection wave generator and said voltage regulator to dynamically energize said convergence field-producing apparatus.

2. In a cathode ray image reproducing system wherein a plurality of electron beam components, which traverse predeflection paths that are spaced respectively about the longitudinal axis of a tube, are angularly deflected both horizontally and vertically by deflection apparatus to scan a raster at a target electrode and having fieldproducing apparatus adjacent to said predeflection paths and energizable to effect substantial convergence of said beam components at all points of said raster, a system to energize said beam convergence field-producing apparatus comprising, a raster scanning substantially sawtooth deflection wave generator coupled to said deflection apparatus, a source of relatively high voltage coupled to statically energize said convergence field-producing apparatus, voltage regulating apparatus connected in shunt with said static convergence voltage source, means coupled to said sawtooth deflection wave generator to produce a beam convergence wave, and means coupling the output of said convergence wave-producing means in'series with said voltage regulating apparatus to dynamically energize said convergence field-producing apparatus.

3. In a cathode ray image reproducing system wherein a plurality of electron beam components, which traverse predeflection paths that are spaced respectively about the longitudinal axis of a tube, are angularly deflected both horizontally and vertically by deflection apparatus to scan a raster at a target electrode and having field-producing apparatus adjacent to said predeflection paths and energizable to cflect substantial convergence of said beam components at all points of said raster, a system to energize said beam convergence field-producing apparatus comprising, a raster scanning substantially sawtooth deflection wave generator, a source of relatively high voltage coupled to statically energize said convergence fieldproducing apparatus, a voltage regulator including an electron tube having its anode-to-cathode circuit connected in shunt with said static convergence voltage source, means coupled to said sawtooth deflectionwave generator to develop a beam convergence wave, and means coupling said convergence Wave-developing means into the cathode circuit of said voltage regulator tube to impress said convergence wave upon said convergence field-producing apparatus for its dynamic energization. V v V 4. In a cathode ray image reproducing system wherein a plurality of electron beam components, which traverse predeflection paths that are spaced respectively about the longitudinal axis of a tube, are angularly deflected both horizontally and vertically by deflection apparatus to scan a raster at a target electrode and having fieldproducing apparatus adjacent to saidpre'deflection paths and energizable to effect substantialiconvergence ofsaid beam components at all points Of'Said raster, a system to energize said beam convergence field-producing apparatus comprising, a raster scanning substantially sawtooth. deflection wave generator comprising an output circuit including an electron tube having an anode and a cathode serving as output electrodes, said anode and cathode circuits being such as to respectively develop sawtooth and parabolic waves, said anode beingcoupled to said deflection wave output circuit, a convergence wave output transformer having primary and secondary windinas, means coupling said primary winding to one of said electron tube output electrodes, a source of voltage coupled to said convergence field-producing apparatus for its static energization, a voltage regulator electron tube connected in shunt with said voltage source, and means coupling said secondary winding to said regulator tube to dynamically energize said convergence field-producing a paratus by a convergencewave of pro-determined orm.

5. Electron beam convergence apparatus as defined in claim 4 wherein, said primary output transformer winding is coupled to the cathode'of said deflection wave output electron tube, whereby to dynamically energize said convergence field-producing apparatus by a wave having a parabolic component.

6. Electron beam convergence apparatus as defined in claim 5 wherein said anode circuit includes decoupling means of a character to develop a parabolic wave L nilar but of opposite phase to said cathode circuit developed parabolic wave, and said primary output transformer winding also is coupled to said anode circuit decoupling means, whereby to' efiect a push-pull energization of said output transformer,

7. Electron beam convergence apparatus as defined in claim 6 wherein, an integrating network is connected across said secondary convergence wave output transformer Winding.

8. Electron beam convergence apparatus as defined in claim 4 wherein, said primary convergence wave output transformer Winding has included in circuit therewith differentiating means, whereby to dynamically energize said convergence field-producing apparatus by a wave having a sawtooth component.

9. In a cathode ray image reproducing system wherein a plurality of electron beam components, which traverse predeflection paths that are spaced respectively about the longitudinal axis of a tube, are angularly deflected both horizontally and vertically by deflection apparatus to scan a raster at a target electrode and having fieldproducing apparatus adjacent to said predeflection paths and energizble to eflect substantial convergence of said beam components at all points of said raster, a system to energize said convergence wave field-producing apparatus comprising, a raster scanning substantially sawtooth deflection wave generator comprising an output circuit including an electron tube having an anode and a cathode serving as output electrodes, the circuits connected to said anode and cathode electrodes being such as to respectively develop sawtooth and parabolic waves, decoupling means in said anode circuit of a character to develop a parabolic wave similar but of opposite phase to said cathode circuit-developed parabolic wave, said anode being coupledto said deflection wave output circuit, a parabolic convergence Wave output transformer having primary'and secondary windings, said primary parabolic wave outputttransformer winding being coupled to the cathode ofsaid deflection wave output electron tube and to said decoupling means, a sawtooth con vergence wave output transformer having primary and secondary windings, differentiating means included in said primary sawtooth wave output transformer windings, said primary sawtooth waveoutput transformer winding being coupled to the cathode of said deflection wave output electron tube and to'said decoupling means, a source of voltage coupled to said convergence field-producing apparatus for its static energization, a voltage regulator electron tube connected in shunt with said voltage source, and means coupling the secondary windings of said parabolic and sawtooth convergence wave output transformers respectively to said regulator tube to dynamically energize said convergence field-producing apparatus by a composite convergence wave having parabolic and sawtooth components.

10. Electron beam convergence apparatus as defined in claim 8 wherein, the primary windings of said convergence wave output transformers are effectively connected in shunt with one another, and the secondary 10 windings of said convergence wave output transformers are connected in series with one another.

11. Electron beam convergence apparatus as defined in claim 9 wherein, a capacitor is connected across the secondary winding of said parabolic convergence wave output transformer.

References Cited in the file of this patent UNITED STATES PATENTS Zworykin et al. Oct. 31, 1939 2,220,303 Tingley Nov. 5, 1940 2,672,574 Evans Mar. 16, 1953 

